1. Field
This application relates to a bowling ball weighing apparatus which provides information about a bowling ball's weight imbalance.
2. Prior Art
Bowling balls can have a mass imbalance between two opposite hemispheres caused by the hemispheres having different masses and/or mass distributions, and this mass imbalance results in a weight imbalance between the two hemispheres. A mass imbalance can be established during manufacturing due to normal manufacturing tolerances or it can be intentionally manufactured into a ball to improve its performance. Also, after a ball is manufactured, it is normally drilled with finger holes, and this will change the ball's as-manufactured mass distribution. The United States Bowling Congress (USBC) has put limits on the allowable weight imbalance of a bowling ball. The rules are a bit complicated, but basically a ball must have its weight imbalance analyzed in three specific orientations, and the weight imbalance of the opposite hemispheres of these orientations must be less than a prescribed maximum value for each orientation.
What is actually being measured when determining weight imbalance is a torque resulting from a mass imbalance; an equivalent mass imbalance times a moment arm. A weight imbalance between a ball's two opposite hemispheres divided by a vertical plane applies a torque about a horizontal axis which lies in the vertical plane and passes through the bowling ball's center, and by custom, one ounce of weight imbalance is equivalent to 3.294 ounce-inches of torque about this axis.
A tool commonly used to determine a bowling ball's weight imbalance is called a dodo weight scale, or dodo balance beam weight scale. It has a ball cradle which can hold a bowling ball in any rotational orientation, it has primary and secondary balance beams, and it has a single pivot point which supports all the weight of the ball, balance beams, ball cradle, and support frame. A ball is placed in the dodo scale's cradle in an orientation specified by the USBC, and with the secondary balance beam set in its zero position, the primary beam is balanced. The ball is then rotated 180 degrees about a vertical axis through its center and the secondary beam is adjusted to again achieve balance. The weight imbalance of the ball's two hemispheres is the reading of the secondary balance beam, and this must be less than that allowed by the USBC for that particular ball orientation. This procedure is repeated two more times in two other USBC specified ball orientations. This dodo balance beam scale requires two balance beams, or essentially two weight scales, for its operation and as stated above, all the weight of the ball is supported at one pivot point.
Another apparatus used to determine a bowling ball's weight imbalance uses two or more electronic load cells to measure a ball's imbalance, and this apparatus is described in U.S. Pat. No. 5,367,129 to Lahl (1994). In this apparatus, a bowling ball is placed in a locating ring which is ultimately supported by two or more electronic load cells. Weight imbalance is determined by comparing the readings of these load cells. This apparatus requires an electronic scale specially designed for this purpose, having two or more load cells with a specially designed load cell analysis routine to determine a bowling ball's weight imbalance. Here again, this apparatus requires the use of two or more weight scales (two or more load cells) for its operation, with portions of the ball's weight supported by each of the scales.
It is desirable to have a bowling ball weighing apparatus which uses a single, commercially available weight scale along with a bowling ball support assembly to determine a bowling ball's weight imbalance.